1. Field of the Invention
This invention relates to a new image forming method and a device for forming images, and particularly, to an image forming method having image display function, image recording function and image display and recording function, and a device therefor. This invention more particularly relates to an image forming method in which a plurality of electrodes are controlled by transistors connected to the electrodes and thereby a toner is selectively attached to the electrodes, and a device therefor.
2. Description of the Prior Art
There are known a wide variety of image forming devices. Various systems have been used for cameras, copiers and printing machines.
In the recent technology of electronics, there are strongly demanded the image forming devices which are easily controlled by electronics (condition-1), require only low voltage and low power (condition-2) and are small in size and light in weight (condition-3).
In addition, innovation of each particular type of image forming devices is requested.
For example, one type of electrophotographic cameras, dream camera, seeks to satisfy the above-mentioned three conditions and use a non-silver salt photosensitive member. This new electrophotographic camera is demanded since silver resources are depleted year by year.
On the other hand, a device for forming images instantly is known as an "instant camera". There are also known simple instant image forming methods utilizing electronic control.
Further, in the case of copying machines, there have been shown recently remarkable advances with respect to small size, light weight and low power consumption, but there are not yet available any truly portable copying machines.
These image forming devices are required to have a function of optionally adding information as well as a function of reproducing originals with high fidelity. In other words, there are desired display of output from language treating devices such as those known as "word processors" and terminal devices capable of converting output of computers or output of telephone and communication circuits to letters, drawings or images.
These devices overlap the devices known as facsimiles or printers. As domestic image forming terminals in future, it is desired that a single output terminal for various imaging signal sources can effect both computer treatment and the conversion without having separate output mechanisms for computer treatment and for communication circuits.
In this sense, safety and easy maintenance are desired. From this point of view, a method employed in conventional copiers for forming images comprising producing latent images corresponding to light images of an original on a photosensitive member of a photoconductor, developing with a toner and transferring the developed images is not suitable for the image formation of external electric signals. In addition, since the conventional copiers require a high voltage at the image transferring step using an electric field and use a photosensitive layer drum, the copiers can not be small in size and portable.
On the other hand, the step of forming latent images of external electric signals has been recently achieved by a laser beam printer, and this step comprises converting electric signals to light signals and conducting the image writing on a photosensitive layer by the light signals. A device having such a mechanism can be used as an image forming device capable of producing rapidly images of high quality, but the device is not easily used as the above-mentioned small type portable image terminal, since a light writing device must be added to a conventional copying machine.
Conventional image forming devices are limited to a mechanism whereby a hard copy is produced, that is, images are formed on paper and the like. However, image forming terminals to be demanded in the future will not always be required to produce finally a hard copy. That is, output visualized information often becomes unnecessary after it has been read. Further, it is not always desired that visualized information to be stored are stored as a hard copy, since wood pulp resources will be depleted when paper is used for the hard copy and besides the resulting hard copy requires increased space for storing.
In view of the foregoing, in case an image forming terminal is required only to show a display function in future, it is desired that the display by the image forming terminal can be erased after the display has been read. Such operation can be effected by various known display devices. However, whatever type the display device is, for example, an active type or a passive type, the display is an optical image, and therefore, if it is desired to have it as a hard copy, a separately provided image forming device is operated or the displayed optical image is projected to an image forming device.
The above-mentioned word processing device can advantageously edit and erase the letter information while producing the letter information, but a lot of memory elements are disadvantageously required if the processing device should temporarily store long sentences for display and writing. In order to decrease the number of memory elements, it is desired that the writing information itself function as the display information and when the whole sentences are completed, the display information itself can be transferred as a hard copy.
Devices satisfying the above conditions are not yet commercially available.
Some devices can effect writing and rewriting for optional images and after that, a hard copy thereof can be obtained. It is desired that such operations can be effected without memory elements corresponding to the whole picture elements, but any device effecting such operations is not commercially available.